The invention relates to a fresh-gas supply device for an internal combustion engine having an exhaust-gas turbocharger and to a method for regulating an outlet pressure of a fresh-gas supply device of such a type.
Internal combustion engines, such as for example diesel engines, are often fitted with exhaust-gas turbochargers. In this regard, FIG. 1 shows a schematic illustration of an internal combustion engine 1, the exhaust line 10 of which is coupled to an exhaust-gas turbocharger 2. The exhaust-gas turbocharger has a turbine 4 which is driven by exhaust gas and which is coupled to a compressor 3. The compressor 3 compresses intake air from an intake air inlet 11 in order to increase an intake pressure in an intake line 9′ for the internal combustion engine 1, as a result of which, for example, acceleration of the vehicle having the internal combustion engine 1 and a reduction in the energy consumption are obtained.
However, the exhaust-gas turbocharger 2 cannot deliver a sufficient quantity of air, and therefore cannot generate a sufficient intake pressure, in all operating states of the internal combustion engine 1. For example, piston engines such as diesel engines having an exhaust-gas turbocharger 2 have, for example, an operating state during acceleration which is referred to as “turbo lag”. Here, the internal combustion engine 1 reacts with a rotational speed increase only after a certain time delay after the accelerator pedal is pressed, during which time delay no exhaust-gas energy is available, that is to say also no sufficient exhaust-gas pressure is available for driving the exhaust-gas turbocharger 2, and therefore no compressed intake air with a corresponding intake pressure is available. To bridge this “turbo lag”, solutions have been proposed in which compressed air, for example from a tank 13, which is fed by an air compressor 14, is introduced in a controlled fashion into the intake line 9′ of the internal combustion engine 1 in order, in the event of an increased intake air demand of the internal combustion engine 1, to cover the demand. This takes place by way of a fresh-gas supply device 7, which is arranged between the compressor 3 of the turbocharger, or a charge-air cooler 5 which is connected downstream in the flow direction, and the intake line 9′.
A fresh-gas supply device 7 is illustrated schematically in FIG. 2. The fresh-gas supply device 7 is connected with a charge-air inlet 6 to the charge-air cooler 5 and with an outlet 9 to the intake line 9′. A flap element 16 is situated between the charge-air inlet 6 and the outlet 9, which flap element 16 can be adjusted by an adjusting motor 17 in order to close off and open the connection from the charge-air inlet 6 to the outlet 9. Furthermore, a compressed-air inlet 8 is connected to the outlet 9 and, via a flow-regulating device 20, to the tank 13.
A control device 15 serves to control the flow-regulating device 20 and the adjusting motor 17. The control device 15 is also connected here to pressure sensors 18 and 19, of which a first pressure sensor 18 measures a pressure of the outlet 9 (outlet pressure) and a second pressure sensor 19 measures a pressure of the charge-air inlet 6 (inlet pressure) and detects a torque demand in the event of a “kick-down”. In this case, the flow-regulating device 20 supplies compressed air by opening the connection from the compressed-air inlet 8 to the outlet 9. The controlled flap element 16 is firstly closed, such that the compressed air does not flow via the charge-air inlet 6 into the compressor 3 of the exhaust-gas turbocharger 2 counter to the intake direction, but rather flows via the outlet 9 into the intake line 9′. When the supply of compressed air is ended, the flap element 16 is opened again and the flow-regulating device 20 is closed. At that time, the inlet pressure is sufficient again as a result of the compressor 3 of the exhaust-gas turbocharger 2.
In this regard, the German laid-open specification DE 10 2006 785 A1 describes an example by way of illustration.
The outlet pressure is adjusted by means of the supply of compressed air, in such a way that no smoke formation can take place on account of an excessively enriched fuel/air mixture. In this way, it is possible to generate a leaner fuel/air mixture than is required, in particular at the start of the supply of compressed air. Consequently, more air is consumed than is required. This can lead to increased power of the air compressor 14 and to additional NOx formation.
It is therefore an object of the present invention to provide an improved fresh-gas supply device and a method for regulating an outlet pressure of a fresh-gas supply device of the above-mentioned type, with the above disadvantages being eliminated or significantly reduced, and with further advantages being created.
According to the invention, a fresh-gas supply device is provided for an internal combustion engine having an exhaust-gas turbocharger comprising a charge-air inlet for the admission of charge air from the exhaust-gas turbocharger; a compressed-air inlet for the admission of compressed air; an outlet which can be connected via an adjusting device, preferably via a flap element, to the charge-air inlet and via a flow-regulating device, which has a closed position and preferably any desired open positions, to the compressed air-inlet, which the flow-regulating device being closed when the flap element is partially open or fully open; and a control device for controlling the adjusting device, preferably the flap element, and the flow-regulating device as a function of operating states of the internal combustion engine, wherein the flow-regulating device has at least one valve for opening and for closing off the compressed-air inlet and has a proportional valve, which is connected downstream in the flow direction, for adjusting an outlet pressure in the outlet.
Further according to the invention, a fresh-gas supply device is provided for an internal combustion engine having an exhaust-gas turbocharger, comprising: a charge-air inlet for the admission of charge air from the exhaust-gas turbocharger; a compressed-air inlet for the admission of compressed air; an outlet which can be connected via an adjusting device, preferably a flap element, to the charge-air inlet and via a flow-regulating device, which has a closed position and any desired open positions, to the compressed-air inlet, with the flow-regulating device being closed when the adjusting device, preferably the flap element, is partially open or fully open; and a control device for controlling the flap element and the flow-regulating device as a function of operating states of the internal combustion engine, wherein the flow-regulating device has at least two valves for opening and for closing off the compressed-air inlet and for adjusting the outlet pressure in the outlet, and with it being possible for the at least two valves to be controlled separately by the control device via in each case one control valve.
Still further according to the invention, a method is provided for regulating an outlet pressure in an outlet of a fresh-gas supply device, the method comprising the steps of: (a) determining an inlet pressure in a charge-air inlet and an outlet pressure in the outlet of the fresh-gas supply device, and operating parameters of an operating state of the internal combustion engine; (b) blocking the connection of the outlet to the charge-air inlet by closing the adjusting device, preferably the flap element, if one determined operating parameter or a plurality require an increased acceleration of the internal combustion engine; (c) opening the connection of the outlet to the compressed-air inlet by opening the at least one valve and the proportional valve during a pressure build-up phase and regulating the outlet pressure by comparing the outlet pressure with a nominal pressure by adjusting the proportional valve during a pressure-regulating phase; and (d) closing the connection of the outlet to the compressed-air inlet by closing the at least one valve and the proportional valve and opening the connection of the outlet to the charge-air inlet by opening the adjusting device, preferably the flap element, if the inlet pressure has reached a defined and parameterizable value.
Yet still further according to the invention, a method is provided for regulating an outlet pressure in an outlet of a fresh-gas supply device the method comprising the steps of: (a) determining operating parameters of an operating state of the internal combustion engine; (b) blocking the connection of the outlet to the charge-air inlet by closing the adjusting device, preferably the flap element, if one determined operating parameter or a plurality require an acceleration of the internal combustion engine; (c) opening the connection of the outlet to the compressed-air inlet by fully opening the at least two valves in a pressure build-up phase and regulating the outlet pressure by comparing said pressure with a nominal pressure during a pressure-regulating phase by separately opening and closing the at least two valves or by adjusting at least one of the at least two valves between an open and closed position; and (d) closing the connection of the outlet to the compressed-air inlet by closing the at least two valves and opening the connection of the outlet to the charge-air inlet by opening the adjusting device, preferably the flap element, if the inlet pressure has reached a defined and parameterizable value.
By use of the at least one valve and the proportional valve connected downstream, it is advantageously possible for the supply of compressed air to be enabled quickly initially, with the proportional valve then being used to regulate the outlet pressure by means of adjustment. Here, there is no excess of pressure, and the fuel/air mixture can advantageously be set to the value required at a respective operating state. The at least one valve is designed to seal off a higher pressure than the proportional valve, as a result of which the proportional valve can be designed to be smaller.
In an alternative design, the fresh-gas supply device for an internal combustion engine having an exhaust-gas turbocharger has the following: a charge-air inlet for the admission of charge air from the exhaust-gas turbocharger; a compressed-air inlet for the admission of compressed air; an outlet which can be connected via a flap element to the charge-air inlet and via a flow-regulating device, which has a closed position and any desired open positions, to the compressed-air inlet, with the flow-regulating device being closed when the adjusting device, preferably the flap element, is partially open or fully open; and a control device for controlling the adjusting device, preferably the flap element, and the flow-regulating device as a function of operating states of the internal combustion engine, with the flow-regulating device having at least two valves for opening and for closing off the compressed-air inlet and for adjusting an outlet pressure in the outlet, and with it being possible for the at least two valves to be controlled separately by the control device via in each case one control valve.
By use of at least two valves, it is advantageously possible to carry out a multi-stage adjustment of the outlet pressure, with it being possible for the valves to be controlled separately via control valves. Here, the valves may have equal or different flow cross sections, thereby enabling flexible adaptation to an adjustment of the required outlet pressure. Here, it is possible for both the activation time and also the number of activated valves to be varied.
In one preferred embodiment, it is provided that the at least one valve and the proportional valve are arranged in a valve housing of a valve module. Even in the case of the multi-stage arrangement with at least two valves, such a module arrangement is advantageous since it offers the possibility of simple exchange and of adaptation to different applications.
In a further preferred embodiment, the proportional valve has a valve disc which is arranged in a flow path between the at least one valve and an outlet opening to the outlet, and can be pivoted by a stepper motor in order to assume the closed position and any desired open positions to close off or to open the flow path. The proportional valve may also have a safety spring which is connected to the valve disc and which exerts a force on the valve disc in the direction of the closed position of the valve disc. As a result of the valve which is connected upstream, it is possible for a proportional valve, which in this case has only a restricted sealing capability for lower pressures than the valve which is connected upstream, to be used primarily for pressure adjustment for a regulation of the outlet pressure, as a result of which installation space is saved. In the event of a failure of the stepper motor, the safety spring returns the valve disc into the closed position.
The at least one valve may be a diaphragm valve which is suitable for installation in a valve module.
The fresh-gas supply device may have at least one pressure sensor for measuring the outlet pressure and at least one pressure sensor for measuring an inlet pressure in the charge-air inlet, as a result of which the respective pressure value can be measured on location and may not be derived from other operating parameters. According to one advantageous variant, the pressure sensors may—though they need not be—integrated directly into the fresh-gas supply device. In an alternative embodiment, suitable measuring devices are arranged outside the fresh-gas supply device in order to measure the inlet pressure and outlet pressure. In a further alternative embodiment, the inlet pressure and outlet pressure can be calculated on the basis of operating parameters by use of suitable algorithms and/or stored table values. Here, the operating parameters may be existing values, for example from a central processor. The algorithms and/or table values may be a constituent part of an item of software of a control unit, for example of the engine control unit.
In a further alternative design, the at least two valves and/or the flap element can be adjusted in a continuously variable fashion between a closed position and an open position by electrical, mechanical and/or other measures. Here, the valves may likewise have equal-sized or different-sized flow cross-sections, thereby permitting a particularly high degree of variability for adjusting or regulating the outlet pressure. It is particularly advantageous if both the two valves and also the flap element are in each case adjustable in a continuously variable fashion, because a large range of adaptation to different operating states is provided in this way.
A method for regulating an outlet pressure in an outlet of a fresh-gas supply device having at least one valve and having a proportional valve connected downstream as described above has the following method steps:
(S1) determining an inlet pressure in a charge-air inlet and an outlet pressure in the outlet of the fresh-gas supply device, and operating parameters of an operating state of the internal combustion engine;
(S2) blocking the connection of the outlet to the charge-air inlet by closing the adjusting device, preferably the flap element, if one determined operating parameter or a plurality require an increased acceleration of the internal combustion engine;
(S3) opening the connection of the outlet to the compressed-air inlet by opening the at least one valve and the proportional valve during a pressure build-up phase and regulating the outlet pressure by comparing the outlet pressure with a nominal pressure by adjusting the proportional valve during a pressure-regulating phase; and
(S4) closing the connection of the outlet to the compressed-air inlet by closing the at least one valve and the proportional valve and opening the connection of the outlet to the charge-air inlet by opening the adjusting device, preferably the flap element, if the inlet pressure has reached a defined and parameterizable value. This value may correspond, for example, to the outlet pressure or may be predetermined.
Here, the nominal pressure may be determined by the control device from the determined operating parameters and pressures on the basis of suitable algorithms and/or stored table values. This may take place in the control device or also in part in a superordinate engine controller. The adjustment of the proportional valve may also be adjusted by the control valve according to a look-up table. In this way, it is ensured that the respectively required fuel/air mixture is correctly set in all operating states of the internal combustion engine during the supply of compressed air, as a result of which there is no increased formation of NOx. Furthermore, as a result of air being saved, the power of the air compressor is not increased and therefore fuel is saved, since the air compressor is either directly connected to the internal combustion engine or is operated indirectly by electrical current, generated by said internal combustion engine, from a generator or a battery.
An alternative method for regulating an outlet pressure in an outlet of a fresh-gas supply device as described above having at least two valves has the following steps:
(S1) determining operating parameters of an operating state of the internal combustion engine;
(S2) blocking the connection of the outlet to the charge-air inlet by closing the adjusting device (closure device), preferably the flap element, if one determined operating parameter or a plurality require an acceleration of the internal combustion engine;
(S3) opening the connection of the outlet to the compressed-air inlet by fully opening the at least two valves in a pressure build-up phase and regulating the outlet pressure by comparing said pressure with a nominal pressure during a pressure-regulating phase by separately opening and closing the at least two valves or by adjusting at least one of the two valves between an open and closed position; and
(S4) closing the connection of the outlet to the compressed-air inlet by closing the at least two valves and opening the connection of the outlet to the charge-air inlet by opening the adjusting device, preferably the flap element, if the inlet pressure has reached a defined and parameterizable value. This value may correspond, for example, to the outlet pressure or may be predetermined.
Here, the supply of compressed air may take place during every demand for acceleration or for a torque increase (also referred to as “kick-down”). It is however also contemplated to use the supply of compressed air only in the event of predefined demands, for example only during certain gearshift processes.
Here, the nominal pressure may be determined by the control device from the determined operating parameters, or from all available operating parameters, on the basis of suitable algorithms and/or stored table values, as a result of which additional pressure sensors on the fresh-gas supply device are not necessary. The operating parameters may even contain such values directly or indirectly. Additional pressure sensors are of course also possible.
The at least two valves may be separately opened and closed, or at least one of the at least two valves may be adjusted between an open and closed position, by the control device according to a look-up table. For example, it is possible for this purpose for a particular activation/deactivation strategy or adjustment strategy to be predefined, and likewise stored in table values. The table values may be stored in the control device and/or externally, for example in the engine controller.
Instead of a flap element, it is also possible to use some other type of adjusting device, for example a slide element.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.